Leukemia inhibitory factor (LIF) is a polypeptide with a broad range of biological effects. LIF was initially purified from mouse cells and identified on the basis of its ability to induce differentiation in and suppress the proliferation of the murine monocytic leukemia cell line M1. Tomida, et al., J. Biol. Chem. 259:10978-10982 (1984); Tomida, et al., FEBS Lett. 178:291-296 (1984). Human LIF (hLIF) subsequently was shown to have comparable effects on human HL60 and U937 cells, particularly when acting in collaboration with GM-CSF or G-CSF colony stimulating factors. Maekawa, et al. Leukemia 3:270-276 (1989).
LIF has been shown to exhibit a variety of biological activities and effects on different cell types. For example, it has been shown to stimulate osteoblast proliferation and new bone formation, Metcalf, et al., Proc. Nat. Acad. Sci., 86:5948-5952 (1989), as well as bone resorption, Abe, et al., Proc. Nat. Acad. Sci. 83:5958-5962 (1986); Reid, et al., Endocrinology 126:1416-1420 (1990), stimulate liver cells to produce acute phase plasma proteins, Baumann, et al., J. Immunol. 143:1163-1167 (1989), inhibit lipoprotein lipase, Mori, et al., Biochem. Biophys. Res. Commun. 160:1085-1092 (1989), stimulate neuronal differentiation and survival, Murphy, et al., Proc. Nat. Acad. Sci. 88:3498-3501 (1991), Yamamori, et al., Science 246:1412-1416 (1989), and inhibit vascular endothelial cell growth, Ferrara, et al., Proc. Nat. Acad. Sci. 89:698-702 (1992). Receptors for LIF have been found on monocyte-macrophages, osteoblasts, placental trophoblasts, and liver parenchymal cells. Hilton, et al., J. Cell. Biochem. 46:21-26 (1991); Allan, et al., J. Cell. Physiol. 145:110-119 (1990); Hilton, et al., Proc. Nat. Acad. Sci. 85:5971-5975 (1988).
Depending upon its particular activity or effect, LIF has been referred to by various names, including differentiation-inducing factor (DIF, D-factor), hepatocyte-stimulating factor (HSF-II, HSF-III), melanoma-derived LPL inhibitor (MLPLI), and cholinergic neuronal differentiation factor (CDF). Hilton, et al., J. Cell. Biochem. 46:21-26 (1991).
Genomic and cDNA clones encoding murine, rat, and human LIF have been isolated. Gearing, et al., EMBO J. 6:3995-4002 (1987); Yamamori, et al., Science 246:1412-1416 (1989); Gough, et al., Proc. Nat. Acad. Sci. 85:2623-2627 (1988).
Antibodies to hLIF are expected to have valuable diagnostic and therapeutic applications, such as in assaying for the presence of hLIF in clinical specimens, and in regulating the biological effects of hLIF and the interaction of hLIF with its receptors and other ligands. In particular, monoclonal antibodies (mAbs) detecting unique epitopes of hLIF would be of great value in understanding and regulating the diverse biological activities of hLIF. Neutralizing mAbs specific for hLIF that inhibit one or more of the biological activities or effects of hLIF have great potential as therapeutic agents useful in the treatment of conditions wherein the presence of hLIF causes or contributes to undesirable pathological effects, such as cachexia, dysregulated calcium metabolism, or excessive bone resorption (such as may be associated with osteoporosis).
Several polyclonal antibodies have been described that react with LIF. Tomida, et al., FEBS Letters 151:281-285 (1983) immunized rabbits with partially purified D-factor from mouse cells, and obtained antibodies capable of neutralizing the activity of mouse D-factor, and to a lesser extent, rat and hamster D-factors, in several assays. Baumann, et al., J. Immunol. 143:1163-1167 (1989) reported that rabbit polyclonal antibodies against hepatocyte-stimulating factor III (HSF-III) neutralized that activity of hLIF on hepatic cells.
There is a need for high affinity monoclonal antibodies to hLIF that are capable of effective inhibition of the biological activities of hLIF. It would be particularly desirable to provide monoclonal antibodies that are effective inhibitors of hLIF binding to its receptors, but which do not interfere with the binding of other factors, such as interleukin 1 (IL-1), interleukin 3 (IL-3), interleukin 6 (IL-6), tumor necrosis factor-.alpha. (TNF-.alpha.), granulocyte CSF (G-CSF), granulocyte-macrophage-colony stimulating factor (GM-CSF), and Oncostatin M.